Image forming apparatuses are used as printers, facsimile machines, copiers, plotters, or multi-functional devices having two or more of the foregoing capabilities. As one type of image forming apparatus employing a liquid-ejection recording method, an inkjet recording apparatus is known that uses a recording head (liquid ejection head) for ejecting droplets of ink. During image formation, such liquid-ejection-type image forming apparatuses eject droplets of ink or other liquid from the recording head onto a recording medium to form a desired image.
Such liquid-ejection-type image forming apparatuses fall into two main types: a serial-type image forming apparatus that forms an image by ejecting droplets from the recording head while moving the recording head in a main scanning direction of the carriage, and a full-line-type image forming apparatus that forms an image by ejecting droplets from a linear-shaped recording head held stationary in the image forming apparatus.
Conventionally, as one type of image forming apparatus that conveys a recording medium by a conveyance belt, for example, JP-2006-232440-A proposes an image forming apparatus including an image forming engine to form an image on a recording medium, a recording-medium conveyance belt disposed opposing the image forming engine to circulate to convey the recording medium, and a return conveyance passage to return the recording medium having an image recorded on the first face by the image forming engine to an upstream side of the image forming engine for duplex printing. In the recording-medium conveyance belt, a returning part for moving the recording medium in a direction that is the reverse of a normal conveyance direction is arranged on a part of the return conveyance passage, and the recording medium is return-conveyed by the returning part. In addition, a bypass passage is provided separately from the recording-medium conveyance belt so as to start from an exit of the return part in the moving direction of the recording medium. The recording medium is returned via the bypass passage onto a part of the conveyance belt moving in the normal conveyance direction.
Similarly, JP-2006-213480-A proposes a recording device including a recording section to eject ink to a recording medium, a conveyance unit to send a recording medium having an image recorded by the recording unit back to an upstream side in a conveyance direction of the recording medium, and a reversing unit disposed downstream from the conveyance unit in a return direction of the recording medium and having a plurality of holding parts to hold a non-recorded face of the recording medium sent back by the conveyance unit, turn around the recording medium, and send the recording medium to the recording section.
In JP-2006-232440-A, a charger is disposed near an entry of the conveyance belt into the return conveyance passage in the moving direction of the recording medium and within a loop of the conveyance belt so as to charge the conveyance belt from the inner surface side of the conveyance belt. However, for such a conveyance unit that charges the conveyance belt to convey the recording medium with the recording medium attached to and held on the conveyance belt by electrostatic force, separation of the recording medium from the conveyance belt can cause the electrostatic adhesion force to decrease or decay. As a result, when the recording medium is sent back again onto the conveyance belt, the recording medium may not adhere properly to the conveyance belt. In addition, in JP-2006-213480-A, the recording medium is sent back with the recording medium adhering to the conveyance belt by electrostatic force and turned around by the reversing unit disposed downstream in the return direction. As a result, when the recording medium is sent to a return point of the conveyance belt, the recording medium tends to be separated from the conveyance belt, thus hampering stable reverse conveyance.
Similar problems attend the art described in JP-2006-232440-A. When the recording medium is sent to the bypass passage from the conveyance belt charged near the entry of the conveyance belt into the return conveyance passage, the recording medium is separated from the conveyance belt and the electrostatic adhesion force of the conveyance belt decays. As a result, when the recording medium is once more sent back onto the conveyance belt, the recording medium does not properly adhere to the conveyance belt, thus hampering stable reverse conveyance.